EP 1789732 discloses a CO2 refrigeration circuit for circulating a refrigerant in a predetermined flow direction, comprising in flow direction a heat-rejecting heat exchanging device, a receiver having a liquid portion and a flash gas portion, and subsequent to the receiver a medium temperature loop and a low temperature loop, wherein the medium and low temperature loops each comprise in flow direction an expansion device, an evaporator and a compressor, the refrigeration circuit further comprising a liquid line connecting the liquid portion of the receiver with at least one of the medium and low temperature loops and having an internal heat exchanging device, and a flash gas line connecting the flash gas portion of the receiver via the internal heat exchanging device with the inlet of the low temperature compressor, wherein the internal heat exchanging device transfers in use heat from the liquid flowing through the liquid line to the flash gas flowing through the flash gas line.
It is an object of the invention to reduce the energy consumption in CO2 cooling systems, a further object is to protect one or more compressors against liquid CO2 in the compressor inlet by heating the suction gas.